1. Field of the Invention
The present invention relates to a pathological diagnosis support apparatus and a pathological diagnosis support method, which extract and measure information necessary for a pathological expert to make a pathological diagnosis using a pathological image showing a stained tissue sample and display the information, and to a storage medium that stores a program that causes a computer execute the method.
2. Description of the Related Art
In recent years, pathological diagnosis support apparatuses that extract and measure information necessary for a pathological expert to make a pathological diagnosis from a pathological image input as a digital color image using, e.g., a microscope or digital camera, etc., and display the information have been proposed, and an example of such apparatuses is disclosed in Japanese Patent Laid-Open No. 2004-286666.
The pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666 includes: nucleus and cytoplasm distribution estimating means for identifying cell nucleus areas and cytoplasm areas, respectively, from a pathological image; glandular cavity distribution extracting means for identifying glandular cavity areas (areas including almost no cell tissues) from the pathological image; cancer site estimating means for determining whether or not cancer cells exist; progression degree determining means for determining the degree of progression of cancer; and image displaying means for displaying, e.g., a distribution map and/or the degree of progression of cancer cells.
A pathological image which is input to the pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666 shows a tissue sample stained with H & E (hematoxylin and eosin). Thus, cell nuclei are stained in blue, cytoplasms are stained in red, and glandular cavities are not stained. As a result, in the pathological image, the cell nucleus areas have the characteristic of exhibiting a large luminance value (value indicating brightness) for blue, the cytoplasm areas have the characteristic of exhibiting a large luminance value for red, and the glandular cavity areas have the characteristic of their luminance value being represented by a value related to white.
In the pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666, first, the nucleus and cytoplasm distribution estimating means identifies cell nucleus areas and cytoplasm areas, respectively, based on the luminance values of the respective pixels constituting a pathological image. Then, the cancer site estimating means determines whether or not a cancer cell area exists in each of regions obtained as a result of dividing the pathological image into a plurality of regions. Here, an operation of the cancer site estimating means to determine whether or not a cancer cell area exists will be described in detail.
The cancer site estimating means calculates the total number of the pixels for a cell nucleus area and a cytoplasm area identified by the nucleus and cytoplasm distribution estimating means. Then, the cancer site estimating means compares the total number of the pixels with predetermined threshold value Ts. If the total number is determined to be equal to or larger than threshold value Ts as a result of the comparison, the cancer site estimating means calculates the N/C ratio (nuclear-cytoplasmic ratio) of the region, which is a value for determining whether or not the region includes cancer cells, using formula (1) indicated below.N/C ratio=(number of pixels for cell nucleus area)/(number of pixels for cytoplasm area)  (1)
The cancer site estimating means, upon calculation of the N/C ratio, compares the calculated N/C ratio with predetermined threshold value Tr. Then, the cancer site estimating means identifies the region as a cancer cell area if the N/C ratio is equal to or larger than threshold value Tr.
When the cancer site estimating means identifies the cancer cell area, the glandular cavity distribution extracting means identifies glandular cavity areas based on the luminance values of the pixels constituting the pathological image. Then, the glandular cavity distribution extracting means measures feature quantities for each identified glandular cavity area, which quantitatively represent the features of the shape of the glandular cavity area. Feature quantities includes, e.g., area, circumferential length, which indicates the length of the contour of a glandular cavity area, and degree of circularity, which indicates similarity to a circular shape.
When the glandular cavity distribution extracting means have measured the feature quantities, the progress degree determining means determines the degree of progression of cancer with regard to glandular cavity areas included in the cancer cell area identified by the cancer site estimating means from among the glandular cavity areas. More specifically, the progression degree determining means compares the feature quantities measured by the glandular cavity distribution extracting means with data indicating feature quantities related to the degrees of progression of the cancer, and selects the degree of progression in the data that exhibits the most similar feature quantities.
Upon the progression degree determining means determining the degree of progression, the image displaying means displays a distribution map for the cancer cell area identified by the cancer site estimating means and/or the degree of progression of cancer determined by the progression degree determining means.
The pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666 enables extraction of a cancer cell area from a pathological image and/or determination of the degree of progression of cancer by means of quantitatively measuring cell nuclei and cytoplasms and measuring the feature quantities of glandular cavities.
Use of the pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666 enables determination of whether or not cancer cells exist and/or of the degree of progression of cancer. However, a pathological image may include benign tumor cells besides cancer cells, which are of a malignant tumor, and normal cells.
In the aforementioned case, when a pathological expert determines whether cells are cancer cells or benign tumor cells from a pathological image, information indicating the features of the structure of the tissue sample such as the manners in which cell nuclei are positioned is an important clue in addition to the aforementioned N/C ratio and the feature quantities of glandular cavities. Also, information indicating whether or not particular kinds of cells, that provide a basis for determining the cells as cancer cells (for example, signet ring cells), exist is an important clue.
In the pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666, such information is not obtained. Thus, the information obtained by the pathological diagnosis support apparatus described in Japanese Patent Laid-Open No. 2004-286666 alone cannot provide sufficient pathological diagnosis support.